Geomechanical Assessment of CO2 Storage Reservoir Integrity Post-closure (GASRIP)

向深层地质构造注入二氧化碳（CO2）是全世界公认的唯一现实的缓解技术，可以减少目前人为二氧化碳排放，到2050年达到国家目标。然而，碳捕集与封存（CCS）引起了公众对地质储层潜在的地表二氧化碳泄漏的担忧，限制了潜在储层的数量。包括英国在内的欧洲国家已经考虑将枯竭的油气田和含盐含水层用于二氧化碳储存（例如北海的Sleipner油田），而美国的一些项目则专注于二氧化碳注入，以提高枯竭或非常规油气储层的采收率（EOR）。地质储层是复杂的体系。注入二氧化碳后，二氧化碳-流体-岩石相互作用会影响其地质力学完整性，这种影响可以用热、水文、机械和化学耦合现象（THMCs）来量化。二氧化碳注入引起的thmc会导致地震活动性的增强和二氧化碳向地表的泄漏。因此，CCS和EOR-CCS技术的出现引发了对在整个二氧化碳储存周期（持续100年）中保持储层地质力学完整性的更多研究的需求。迄今为止，研究人员主要关注的是二氧化碳注入过程中储层物性的变化（从含盐水地层过渡到含二氧化碳地层）以及相关的超压效应。一般认为，CO2注入中断后，储层压力降低，CO2羽流运移，自然吸胀导致含水层回灌。然而，CO2注入是一个干燥过程，在盐水饱和地层中会引发复杂的盐沉淀现象。一些研究集中在孔隙度和渗透率降低与注入效率和储存能力相关的风险上。一个鲜为人知的事实是，在封闭条件下生长的盐晶体有可能通过施加巨大的压力（破盐作用）来破坏岩石。停止CO2注入后，含水层回灌导致盐溶解和储层压实。在二氧化碳储存环境下盐沉淀的假设可逆性还有待研究。在注入二氧化碳后的自然含水层补给过程中，我们预计哪些现象会影响储层的完整性？我们能控制他们吗？随着我们向低碳世界迈进，能源行业正在转型；CCS和EOR-CCS正在成为石油和天然气行业的重要实践，石油和天然气行业是英国经济的重要部门。解决这些问题对于在英国减少温室气体排放所需的规模上进行安全的CCS操作至关重要，同时提高油气储层（如英国北海油田）的采收率。该项目旨在通过降低CCS风险，并提供一种可能的新EOR方法，解决英国工业战略的清洁能源议程。封存后CO2储层完整性地质力学评价（GASRIP）项目主要研究CO2盐水诱导的盐沉淀/溶解对CO2储层地质力学完整性的影响。通过在实验室中观察天然砂岩的弹性、力学和输运特性的变化，GASRIP将评估注入二氧化碳后含盐硅油储层力学特性的变化。通过分析富含碳酸盐的砂岩，GASRIP将确定二氧化碳注入后对化学反应性储层的机械和化学影响。这些信息对于以可控的方式使用盐沉淀来改善致密储层的运移特性和可行的油气产量（EOR替代方案）是必要的。通过将结果整合到一个数值模型中，GASRIP将为关闭后的CO2储层风险评估提供一个有价值的工具。

Injecting carbon dioxide (CO2) into deep geological formations is recognized worldwide as the only realistic mitigation technology that can reduce current anthropogenic CO2 emissions to meet national targets by 2050. However, Carbon Capture and Storage (CCS) have aroused public concerns over potential surface leakage of CO2 from geological reservoirs, limiting the number of potential storage sites. European countries, including the UK, have considered depleted oil and gas fields and saline aquifers for CO2 storage (e.g. Sleipner field, North Sea), while a number of projects in the United States have focused on CO2 injection for enhanced oil recovery (EOR) in depleted or unconventional hydrocarbon reservoirs.Geological reservoirs are complex systems. Their geomechanical integrity can be affected by CO2-fluid-rock interactions following injection of CO2, which can be quantified in terms of Thermal, Hydrological, Mechanical and Chemical coupled phenomena (THMCs). THMCs induced by CO2 injection can lead to detrimental enhanced seismicity and CO2 leakage to the surface. So, the advent of CCS and EOR-CCS operations has triggered the need for more research to preserve the geomechanical integrity of reservoirs during the whole CO2 storage cycle (lasting 100s years). To date, researchers have focused on the induced changes in the physical properties of the reservoir during CO2 injection (transition from brine-bearing to CO2-bearing formations) and associated overpressure effects. It is generally assumed that following the interruption of CO2 injection, the reservoir pressure decreases, the CO2 plume migrates and natural imbibition leads to aquifer recharge. However, CO2 injection is a drying process that triggers complex salt precipitation phenomena in brine saturated formations. Several studies have focused on the risks associated with porosity and permeability reduction with respect to injection efficiency and storage capacity. A less appreciated fact is that salt crystals growing under confinement have the potential to damage the rock by exerting enormous pressures (haloclasty). After ceasing the CO2 injection, the aquifer recharge leads to salt dissolution and reservoir compaction.The hypothesized reversibility of salt precipitation in CO2 storage contexts has yet to be investigated. Which phenomena do we expect to affect reservoir integrity during the natural aquifer recharge post-CO2 injection? Can we control them? The energy industry is transforming as we move to a lower carbon world; CCS and EOR-CCS are becoming essential practices for the oil and gas industry, a vital sector for the UK economy. Addressing these questions is crucial for the safe CCS operation at the scales needed to mitigate greenhouse gas emissions for the UK, and at the same time improving recovery rates from hydrocarbon reservoirs (e.g., UK North Sea fields). This project seeks to address the UK Industrial Strategy's clean energy agenda by reducing CCS risks, and providing a possible new EOR method.Geomechanical Assessment of CO2 Storage Reservoir Integrity Post-closure (GASRIP) is a project primarily designed to study how CO2-brine induced-salt precipitation/dissolution affects geomechanical integrity of CO2 storage reservoirs. By looking at changes in the elastic, mechanical and transport properties of natural sandstones in the laboratory, GASRIP will assess variations in the mechanical properties in saline siliciclastic reservoirs post-CO2 injection. By analysing carbonate-rich sandstones, GASRIP will determine the mechanical and chemical post-CO2 injection effects on chemically reactive reservoirs. This information is needed for the potential use of salt precipitation in a controlled manner to improve the transport properties and the viable production of oil and gas from tight reservoirs (EOR alternative). By integrating the results in a numerical model, GASRIP will offer a valuable tool for risk assessment of CO2 storage reservoirs post-closure.